Electronic prescribing (ePrescribing) has the potential to greatly improve the safety, quality and cost-effectiveness of providing medications to patients and to reduce societal medication costs. However, implementation of outpatient ePrescribing also presents many challenges due to the complexity of the medication prescribing system and the requirements for accurate and seamless interoperable health data transmission standards. Furthermore, ePrescribing will also likely create new errors. Realizing the projected benefits of outpatient ePrescribing systems will greatly depend on the functional characteristics of these systems and how well they are integrated into clinical practice. Electronic prescribing transmission standards will play an integral role towards successfully achieving the functional capabilities that are required for safe, reliable, efficient and effective ePrescribing. In this pilot project, we propose to participate in the evaluation of initial standards that will be used to create the final set of adopted foundation standards and ultimately become the final uniform standards, and to catalogue issues that arise in implementation of the standards, and to propose improvements to address those issues. To test the 17 business-to-business transactions as well as the transmission standards' impact on safety, quality and efficiency as outlined in the RFA, we will implement a community utility for ePrescribing which we call the eRx Gateway. This gateway will be a standards-based, open source, middleware messaging engine that connects physician using ePrescribing applications with providers of ePrescribing services i.e. eligibility checking, formulary enforcement, prescription routing and medication history retrieval. This pilot will address the aspects of standards testing described in the RFA: 1) assuring that vocabularies and or code sets that are used for prescribing medications effectively and unequivocally communicate the correct and necessary information from the "sending" physician or other prescribing clinician to the "receiving" patient; and 2) providing a detailed assessment of how the communicated information flows into the business processes as useful and usable data and how the standards affects physician practice processes. We will use the term computerized physician order entry (CPOE) to describe the process of entering medication orders or prescriptions into a computer. Often the computer provides clinical decision support (CDS) to enhance the safety, quality, and occasionally cost-effectiveness, of medication prescribing. In the outpatient setting, CPOE has most been used as a strand-alone system without direct links to outside systems such as pharmacies or pharmacy benefit managers (PBMs). In this proposal, we will define electronic prescribing, or ePrescribing, as medication prescribing using an outpatient CPOE system that electronically exchanges prescriptions and prescription-related information with the pharmacy and/or PBM. The team of investigators participating in this project has the necessary experience and expertise that is required to successfully test ePrescribing standards. The team and their respective organizations include experts and researchers in health information technology, transmission vocabularies and standards, electronic health records, computerized order entry, medication safety and process and workflow evaluations. The evaluation team led by Drs. Rothschild, Bates and Gandhi has extensive experience in medication error research, and in evaluation of healthcare information technology, and the technical team led by Dr. Halamka previously created NEHEN, the New England Healthcare Electronic Data Interchange Network, which has been an extremely successful effort to improve the exchange of administrative healthcare data. Implementation of NEHEN has changed the way that administrative processes are performed in member organizations. NEHEN now generates over 2.5 million transactions a month. The net effect has been that NEHEN members have substantially driven down the costs of administrative overload, while at the same time attaining HIPAA compliance despite the huge transaction volume. The success of NEHEN makes it more likely that this effort will be successful, since it and other efforts have convinced organizations in this area of the benefits of collaborating in the area of HIT interoperability.